1. Technical Field
The present invention relates to a sensor device and, more particularly, to a sensor device in which a sensor section and a circuit section are formed on the same substrate.
2. Related Art
Of sensor devices having a monolithic structure in which a sensor section and a circuit section are formed on the same substrate, a sensor device configured to prevent the circuit section from being contaminated is disclosed in Patent Document 1.
In a sensor device (MEMS microphone) disclosed in Patent Document 1, a sensor section (“MEMS device 200” in Patent Document 1) is provided in a center of an upper surface of the substrate, and a circuit section (“driving/sensing circuitry 300” in Patent Document 1) is provided around the sensor section. At a boundary between the sensor section and circuit section, a barrier structure (“barrier 500” in Patent Document 1) is provided so as to fully surround the sensor section. Thus, providing the barrier structure between the sensor section and circuit section prevents contamination (ion, etc.) from being transferred from the sensor section to circuit section and further prevents moisture or foreign substances that have entered the sensor section from an external environment from entering the circuit section.
In the sensor device disclosed in Patent Document 1, the barrier structure is provided at the boundary between the circuit section and sensor section, so that protective effect can be seen against interference between the circuit section and sensor section in a direction parallel to a substrate surface, particularly, against movement of contamination, such as ion or foreign substances, between the circuit section and sensor section.
However, such a barrier structure does not have effect of protecting the circuit section from disturbance coming from a direction perpendicular to the upper surface of the substrate. Further, the barrier structure does not have the protective effect also against disturbance entering the circuit section from a side of surface side of the substrate. When disturbance such as an electromagnetic wave, light, moisture, or impurities (ion) enters the circuit section from the direction perpendicular to the substrate or the side of surface side of the substrate, adverse effect such as characteristic degradation, malfunction, or failure may occur in the circuit section.
In the case of a general electronic circuit (semiconductor integrated circuit), there is adopted a method that resin-seals the entire circuit section with a molded package so as to protect the circuit section from disturbance from an external environment. However, in a case where the sensor section such as a microphone is provided on the same substrate as the circuit section, a package having a hollow structure is required so as to detect acoustic vibration. In addition, in order to introduce the acoustic vibration into the package, an opening needs to be formed in the package. Thus, in a sensor device having the monolithic structure in which the circuit section and sensor section such as the microphone are formed on the same substrate, it is difficult to cover the entire sensor device with resin for sealing. Further, in the monolithic structure, covering only the circuit section with resin may involve a risk that the resin adheres to the sensor section to obstruct operation of the sensor section and, thus, application of the above-described method to the monolithic structure is difficult. Such a situation is the same with a sensor device in which a sensor section other than the microphone is mounted.
Patent Document 1: U.S. Pat. No. 7,863,714 (FIG. 1)